摘要:

AbstractDialysed haemolymph from the planktonic larvae of the Norwegian lobsterNephrops norvegicuspossessed a lower O2affinity than the benthic adult stage at equivalent pH. This difference could be correlated with the ability to maintain O2uptake during progressive hypoxia; adult individuals showed better developed regulation than the larvae. The intrinsic O2affinity of both larval and adult haemocyanin (Hc) could be modified by preexposure to chronic hypoxia. In contrast, there were no significant differences noted in either Hc O2affinity or the ability to regulate O2uptake during progressive hypoxia between newly hatched and adult individuals of the direct developing amphipodEchinogammarus pirloti. Unlike the case inN. norvegicuspreexposure to chronic hypoxia did not result in any change in respiratory performance at the level of the whole animal or in intrinsic Hc O2affinity. The changes (or absence of them) in these aspects of the respiratory biology of the two species examined are discussed in the context of their ecological requirements. © 1995 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402720602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of cortisol and thyroid hormones on the activity of mitochondrion‐rich (MR) cells in the yolk‐sac membrane of tilapia (Oreochromis mossambicus) embryos and larvae was investigated. MR cells were identified by the fluorescent mitochondrial stain DASPEI. Yolk‐sac membranes from 4‐day‐old embryos in fresh water (FW) were incubated for 24 h in medium supplemented with cortisol, thyroxine (T4), or triiodothyronine (T3). Treatment with cortisol at 0.1 μ/ml and higher significantly increased the population of MR cells and the intensity of fluorescence compared with the control, whereas MR cell size was not affected. Treatments with T4and T3did not affect MR cell density, size, or intensity of fluorescence.Four‐day‐old embryos in FW were immersed for 10 days in FW supplemented with cortisol, T4, or T3. A significant increase in MR cell size was observed starting on day 3 after treatment with 100 μ/ml cortisol. Treatment with lower doses of cortisol produced increases in the cell size on later days. Density of MR cells was significantly increased only on day 9. Treatment with T4produced inconsistent results. Treatment with T3did not affect MR cell size or density at any time. None of the three hormones affected the intensity of fluorescence of MR cells. The stimulatory activity of cortisol on MR cells in the yolk‐sac membrane suggests that cortisol, present in the yolk of tilapia embryos and larvae, may be involved in osmoregulation during the early life stages of fish. © 19

ISSN:0022-104X    

DOI:10.1002/jez.1402720603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe studied effects of temperature on the deiodinating enzymatic pathways governing hepatic production of 3,5,3′‐triiodo‐L‐thyronine (T3) from L‐thyroxine (T4) in rainbow trout. Kinetics of outer‐ring deiodination (ORD) and inner‐ring deiodination (IRD) of T4and T3were measured in vitro at 4°, 12°, and 18°C using liver microsomes of trout that were acclimated for 21 days at 4°, 13°, and 18°C and fed on temperature‐compensated food rations. For all temperatures the Vmax(level of functional enzyme) and Vmax/Km(index of enzyme efficiency) values for the T3‐generating T4ORD pathway greatly exceeded values for the T3‐degrading T3IRD pathway; T4IRD and T3ORD pathways were negligible. The main effects of temperature occurred between 4°C and 12°/13°C; T4ORD Vmax/Kmrose from 0.48 at 4°C to 1.62 at 12°/13°C and to 1.83 at 18°C. This response correlated with in vivo deiodination rates measured previously. T4ORD apparent Kmdid not change over the temperature acclimation range, suggesting an absence of temperature‐induced isozymes. However, Kmwas depressed at the assay temperature of 4°C, indicating a direct effect of temperature to enhance enzyme‐T4substrate affinity. T4ORD Vmaxwas insensitive to assay temperature but was depressed in trout acclimated at 4°C. We conclude that from 4° to 18°C T4ORD is the main thyroid hormone deiodinating pathway in trout liver. T4ORD activity increases more than threefold from 4° to 13°C. This is due to a direct effect of temperature to decrease Kmand to an acclimator

ISSN:0022-104X    

DOI:10.1002/jez.1402720604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPelage cycles of ferrets are poorly documented, although it is clear that their timing is sensitive to daylength, mediated by pineal melatonin. Hair follicles were monitored histologically in ferrets from 3 to 19 months of age in order to describe naturally occurring changes in follicle growth status and follicle number over three successive cycles of fur growth. Melatonin was administered to some of these animals in late summer to determine the long‐term effects of perturbation of hormonal control. Circulating melatonin was elevated for approximately 50 days by 8‐mg continuous release implants. Treated animals grew both their first winter coat, and subsequent summer coats 18 days in advance of untreated controls, but this effect did not extend to the second winter coat. Reimplantation the following year induced an advancement of the autumn follicle growth as in the 1st year. Autumn fiber growth occurred at similar times in untreated males and females, and response to melatonin did not differ between sexes. Hair follicle regression and shedding during the natural spring molt was also contemporaneous in males and females, but fiber regrowth occurred 4–6 weeks later in males as compared with females, suggesting that reproduction‐related factors affect fiber growth initiation, and that fiber growth and shedding are physiologically distinct processes. Melatonin implants in autumn also affected reproduction in the spring, advancing oestrus by 3–4 weeks. These results show that interference with photoperiodic and hormonal control mechanisms in ferrets can affect pelage and reproductive cycles for up to 10 months. © 1995 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402720605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn most sheep breeds, wool growth varies seasonally and is correlated with changes in photoperiod, temperature, and nutrition. Wool growth regulation by these factors may result from systemic changes, or to a response localized at the wool follicle. Possible roles of systemic and local factors have been examined here by comparison of wool growth responses in vivo and in vitro.Wool follicles were isolated and maintained under conditions facilitating fibre growth for at least 4 days. The wool growth rate by follicles isolated regularly over a 10 month period was invariate (P>0.10), in contrast to a seasonally varying wool growth rate by follicles from the same animals in vivo (P<0.001). Although a high energy, high protein diet increased wool growth in vivo (P0.10). It is concluded that selective breeding of domesticated sheep has suppressed the response of follicles to regulation by prolactin and melatonin. Studies currently underway using in situ RT‐PCR will provide further characterization of this conclusion. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402720606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractRegeneration of walking legs in the fiddler crabUca pugilatorrepresents true epimorphic growth since it involves organization of an undifferentiated blastema prior to regrowth of a new limb. Normal regeneration inUcaconsists of two major stages—basal growth and proecdysial growth. One of the earliest events in the basal growth stage of regeneration is the secretion of cuticle by epidermal cells that migrate under the scab at the site of limb loss. When crabs are maintained in a 0.05 mM emulsion of retinoic acid (RA) in sea water during the first 2 weeks following autotomy, the pattern of cuticle secretion is disrupted in many limb buds. Limb buds on RA‐treated crabs grow more slowly and are frequently malformed. © 1995 Wiley‐Lis

ISSN:0022-104X    

DOI:10.1002/jez.1402720607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractArm regeneration in the crinoid echinodermAntedon mediterraneacan provide a very useful model for studying regenerative development. This process can be described as an epimorphic process in which new structures develop from migratory actively proliferating cells. Both the repair and the regenerative phases are due to this fundamental mechanism, which is the only way of recruiting cells to form the cicatricial layer and the blastema. In order to identify the source, the proliferation sites and the recruitment times of these cells, cell proliferation was monitored by employing an immunocytochemical system to detect the thymidine analogue bromodeoxyuridine (BrdU) incorporated by S‐phase cells of the regenerating tissues. On the basis of BrdU incorporation the actively proliferating elements can be identified both close and far from the amputation 1) in the populations of migratory cells which are produced at the level of the brachial nerve and the coelomic wall and 2) in the coelomic epithelium itself. These structures are preferential sources of new cells and give a differential contribution during the repair and the regenerative phases in terms of potential of cell proliferation. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402720608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe distribution of fibroblast growth factor (FGF) in the testes ofSalvelinus leucomaenisandOryzias latipeswas investigated by immunofluorescence staining. InS. leucomaenis, spermatogonia were strongly stained in the infantile testis. When human chorionic gonadotrophin (HCG) was injected into individual fish, the uptake of 5‐bromo 2′‐deoxyuridine (BrdU) occurred within a day. At the same time, FGF became undetectable in spermatogonia, but appeared for the first time around the testicular somatic cells. A similar distribution was seen in the mature testes ofS. leucomaenisandO. latipes. The positively immunostained area corresponded to the predominant site of the Sertoli cells. This pattern of distribution of FGF suggests that FGF plays an important role in the initiation and progression of spermatogenesis in the teleostean testis. © 1995 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402720609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMicroinjection through the tough vitelline coats of oocytes from three molluscan species (Haliotis rufescens, Norrisia norrisi, andAstrea undosa) was facilitated by the local application of sperm vitelline coat lysin with a micropipet. Extracts containing lysin were the 12,000gsupernates of frozen‐thawed sperm. InH. rufescensandN. norrisi, lysin extracts dissolved a small hole through the vitelline coat, whereas inA. undosa, the lysin created a pathway for microinjection by softening the vitelline coat without dissolving it. Similar effects were observed when oocytes were suspended in lysin extracts: Vitelline coats dissolved completely inH. rufescens(previously reported by Lewis et al. [1982], Dev. Biol.92:227–239) andN. norrisi, but only softened and swelled inA. undosa(although they could then be removed by mechanical agitation). The lysin extracts were highly species specific and had no visible effects on heterologous vitelline coats even at concentrations higher than those required to dissolve/soften homologous coats. Evidence thatN. norrisilysin acts by a non‐enzymatic mechanism was provided by the observation that mobilities of radioactive bands in sodium dodecyl sulfate polyacrylamide gels were unchanged following dissolution of125I‐labeled vitelline coats. Electron micrographs of the previously undescribed sperm fromN. norrisiandA. undosaare also presented. © 1995 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402720610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn previous studies, the lingual salt glands of crocodiles have failed to secrete in response to a salt load. This is unlike salt glands in other reptiles and in birds, and it has led to some doubt about the extent to which the salt glands in crocodiles are of functional importance.Believing that the failure to secrete may be associated with the artificial restraint associated with measurement, or with the removal of study animals from the water, we designed and built an electronic sensor which would monitor secretions from the salt glands of crocodiles while they were in water and undisturbed.Under these conditions, the salt glands were observed to secrete spontaneously. Under salt loading, delivered via a femoral vein cannula, there was a rapid production of secretion from the glands. Secretion was stimulated by methacholine and acetylcholine chlorides also. The results support the view that the lingual salt glands in crocodilians are stimulated by a salt load and that previous attempts to demonstrate this may have been influenced by the experimental conditions. © 1995 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402720611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY